1. Field of the Invention
The present invention relates to a printing method, a printing apparatus, and a computer readable non-transitory recording medium storing a printing program.
2. Description of the Related Art
TD printing (Thermal Distend) is known as one of foam molding techniques. The TD printing is a texture expressing technique capable of expressing various shadows or real texture with a distendable sheet by forming undulations or minute irregularities on a surface thereof. For example, one example of the foam molding technique is disclosed in JP 2001-150812 A.
According to the technique disclosed in JP 2001-150812 A, a visible plane image, such as a color image, is formed on a surface of a distend layer of a distendable sheet which includes many microcapsules to be expanded by heating. Next, a light absorbing pattern of a gradation image based on distance image data or the like expressing a stereoscopic shape relative to the plane image is formed on a surface of a substrate corresponding to a reverse surface of the distend layer of the distendable sheet. Then, by irradiating the pattern with a light source from a substrate layer side, heat according to gradation of the image is generated and the microcapsules inside the distend layer are expanded. As a result, protrusions having predetermined heights are formed in the plane image, thereby enabling the expression of texture.
A procedure of the TD printing is outlined as follows. First, a TD image for distending is printed on a TD paper with a toner containing carbon black to generate a gray image for distending. Then, the TD paper is heated by a light source, such as a halogen lamp, and the TD paper distended to hide the gray image for distending is printed with white. Finally, a color image for finishing is printed thereon, thereby generating the color image expressing a texture having irregularities.
Incidentally, according to the above-described conventional TD printing, the image may be distorted by irregularities of distending. Therefore, if the color image for finishing is printed thereon, there has been a problem in that distending occurs and the color image is displaced. For example, FIG. 13A illustrates an image of the printing displacement. For comparison, FIG. 13B illustrates an image in a case where printing displacement does not exist. FIGS. 13A and 13B both illustrate a character “T” (deformed) which comparatively easily causes printing displacement in the TD printing.
In FIG. 13A, a gray portion is an image of a protruding part after distending, and a black portion is a finished print after distending. FIG. 13C illustrates a cross-section of the image illustrated in FIG. 13A. As illustrated, it can be understood that the finished print and the distending portion are displaced. On the other hand, in the comparative example illustrated in FIG. 13B, since the finished print and the distending portion overlap, the distending (gray) portion does not appear.